// PendingBuffer.cs
//
// Copyright (C) 2001 Mike Krueger
// Copyright (C) 2004 John Reilly
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 2001 Free Software Foundation, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.

using System;

namespace ICSharpCode.SharpZipLib.Zip.Compression 
{
    
    /// <summary>
    /// This class is general purpose class for writing data to a buffer.
    /// 
    /// It allows you to write bits as well as bytes
    /// Based on DeflaterPending.java
    /// 
    /// author of the original java version : Jochen Hoenicke
    /// </summary>
    public class PendingBuffer
    {
        #region Instance Fields
        /// <summary>
        /// Internal work buffer
        /// </summary>
        byte[] buffer_;
        
        int    start;
        int    end;
        
        uint   bits;
        int    bitCount;
        #endregion

        #region Constructors
        /// <summary>
        /// construct instance using default buffer size of 4096
        /// </summary>
        public PendingBuffer() : this( 4096 )
        {
        }
        
        /// <summary>
        /// construct instance using specified buffer size
        /// </summary>
        /// <param name="bufferSize">
        /// size to use for internal buffer
        /// </param>
        public PendingBuffer(int bufferSize)
        {
            buffer_ = new byte[bufferSize];
        }

        #endregion

        /// <summary>
        /// Clear internal state/buffers
        /// </summary>
        public void Reset() 
        {
            start = end = bitCount = 0;
        }

        /// <summary>
        /// Write a byte to buffer
        /// </summary>
        /// <param name="value">
        /// The value to write
        /// </param>
        public void WriteByte(int value)
        {
#if DebugDeflation
            if (DeflaterConstants.DEBUGGING && (start != 0) )
            {
                throw new SharpZipBaseException("Debug check: start != 0");
            }
#endif
            buffer_[end++] = unchecked((byte) value);
        }

        /// <summary>
        /// Write a short value to buffer LSB first
        /// </summary>
        /// <param name="value">
        /// The value to write.
        /// </param>
        public void WriteShort(int value)
        {
#if DebugDeflation
            if (DeflaterConstants.DEBUGGING && (start != 0) )
            {
                throw new SharpZipBaseException("Debug check: start != 0");
            }
#endif
            buffer_[end++] = unchecked((byte) value);
            buffer_[end++] = unchecked((byte) (value >> 8));
        }

        /// <summary>
        /// write an integer LSB first
        /// </summary>
        /// <param name="value">The value to write.</param>
        public void WriteInt(int value)
        {
#if DebugDeflation
            if (DeflaterConstants.DEBUGGING && (start != 0) )
            {
                throw new SharpZipBaseException("Debug check: start != 0");
            }
#endif
            buffer_[end++] = unchecked((byte) value);
            buffer_[end++] = unchecked((byte) (value >> 8));
            buffer_[end++] = unchecked((byte) (value >> 16));
            buffer_[end++] = unchecked((byte) (value >> 24));
        }
        
        /// <summary>
        /// Write a block of data to buffer
        /// </summary>
        /// <param name="block">data to write</param>
        /// <param name="offset">offset of first byte to write</param>
        /// <param name="length">number of bytes to write</param>
        public void WriteBlock(byte[] block, int offset, int length)
        {
#if DebugDeflation
            if (DeflaterConstants.DEBUGGING && (start != 0) ) 
            {
                throw new SharpZipBaseException("Debug check: start != 0");
            }
#endif
            Array.Copy(block, offset, buffer_, end, length);
            end += length;
        }

        /// <summary>
        /// The number of bits written to the buffer
        /// </summary>
        public int BitCount {
            get {
                return bitCount;
            }
        }
        
        /// <summary>
        /// Align internal buffer on a byte boundary
        /// </summary>
        public void AlignToByte() 
        {
#if DebugDeflation
            if (DeflaterConstants.DEBUGGING && (start != 0) ) 
            {
                throw new SharpZipBaseException("Debug check: start != 0");
            }
#endif
            if (bitCount > 0) 
            {
                buffer_[end++] = unchecked((byte) bits);
                if (bitCount > 8) {
                    buffer_[end++] = unchecked((byte) (bits >> 8));
                }
            }
            bits = 0;
            bitCount = 0;
        }

        /// <summary>
        /// Write bits to internal buffer
        /// </summary>
        /// <param name="b">source of bits</param>
        /// <param name="count">number of bits to write</param>
        public void WriteBits(int b, int count)
        {
#if DebugDeflation
            if (DeflaterConstants.DEBUGGING && (start != 0) ) 
            {
                throw new SharpZipBaseException("Debug check: start != 0");
            }

            //          if (DeflaterConstants.DEBUGGING) {
            //              //Console.WriteLine("writeBits("+b+","+count+")");
            //          }
#endif
            bits |= (uint)(b << bitCount);
            bitCount += count;
            if (bitCount >= 16) {
                buffer_[end++] = unchecked((byte) bits);
                buffer_[end++] = unchecked((byte) (bits >> 8));
                bits >>= 16;
                bitCount -= 16;
            }
        }

        /// <summary>
        /// Write a short value to internal buffer most significant byte first
        /// </summary>
        /// <param name="s">value to write</param>
        public void WriteShortMSB(int s) 
        {
#if DebugDeflation
            if (DeflaterConstants.DEBUGGING && (start != 0) ) 
            {
                throw new SharpZipBaseException("Debug check: start != 0");
            }
#endif
            buffer_[end++] = unchecked((byte) (s >> 8));
            buffer_[end++] = unchecked((byte) s);
        }
        
        /// <summary>
        /// Indicates if buffer has been flushed
        /// </summary>
        public bool IsFlushed {
            get {
                return end == 0;
            }
        }
        
        /// <summary>
        /// Flushes the pending buffer into the given output array.  If the
        /// output array is to small, only a partial flush is done.
        /// </summary>
        /// <param name="output">The output array.</param>
        /// <param name="offset">The offset into output array.</param>
        /// <param name="length">The maximum number of bytes to store.</param>
        /// <returns>The number of bytes flushed.</returns>
        public int Flush(byte[] output, int offset, int length) 
        {
            if (bitCount >= 8) {
                buffer_[end++] = unchecked((byte) bits);
                bits >>= 8;
                bitCount -= 8;
            }

            if (length > end - start) {
                length = end - start;
                Array.Copy(buffer_, start, output, offset, length);
                start = 0;
                end = 0;
            } else {
                Array.Copy(buffer_, start, output, offset, length);
                start += length;
            }
            return length;
        }

        /// <summary>
        /// Convert internal buffer to byte array.
        /// Buffer is empty on completion
        /// </summary>
        /// <returns>
        /// The internal buffer contents converted to a byte array.
        /// </returns>
        public byte[] ToByteArray()
        {
            byte[] result = new byte[end - start];
            Array.Copy(buffer_, start, result, 0, result.Length);
            start = 0;
            end = 0;
            return result;
        }
    }
}   
